Because of the small size of semiconductors in the manufacturing of semiconductors it is critical that particles and other contaminates not be permitted to contaminate the process. Particles as small as 0.1 μm can contaminate the process and cause defects on the silicon wafers. The first generation of semiconductor manufacturing facilities were built with the so-called open ballroom concept. Here an attempt to keep the entire facility free of particles and other contaminates was made. Each successive generation of manufacturing facility design has made the clean space where particles and other contaminates are eliminated smaller and smaller. The latest design of manufacturing facility has what are called minienvironments. These environments are just big enough to contain the tools that work on the silicon wafers. Silicon wafers are transported from tool to tool in transport pods that attach to the tools in a process that is analogous to two space ships docking. The transport pods are meant to provide the silicon wafers with a protective environment. The silicon wafers are either being processed by a tool, being loaded into or out of a tool, being transported, or being stored. The transport pods are sealed; however, such things as temperature and electromagnetic flux as well as particles can cause defects on the silicon wafers.
Two different types of transport pods are used. The first type is referred to as a SMIF (Standard Machine Interface Pod). These transport pods are designed for use on silicon wafers with diameters of 200 mm and less. The second type of pod is referred to as FOUP (Front Opening Unified Pod). FOUP's are for wafers of 300 mm only.
There are multiple reasons why a silicon wafer may fail to be manufactured properly. Among the reasons are contaminates and poorly calibrated tools. Knowing the environment that a silicon wafer was exposed to during the manufacturing process provides information that can lead to greater yields by narrowing the possible reasons for failures or successes. Further, by monitoring the environment a silicon wafer is exposed to during the manufacturing process, contaminates that may be harming the process can be identified before more wafers are contaminated.
There are methods for sampling the transport pods and the minienvironments; however, these are invasive procedures that require the pods' seal to be opened or the minienvironment to be compromised to allow access to the sampling system.
Thus a need has been established for a device that can monitor the environment that wafers are exposed to throughout the manufacturing process without the need to penetrate the protective environment of the transport pod or the minienvironment.